Smoke detector



Aug. 5, 1969 R. J. SMITH ETAL 3,4(50,l24

SMOKE DETECTOR Filed June 6. 1966 2 Sheets-Sheet 1 22 a? ZZ W/VJW/W z wwazqz was: J nW was 8 .25

Aug. 5, 1969 R. J, 5M|TH ET AL 3,460,124

SMOKE DETECTOR 2 Sheets-Sheet 2 Filed June 6. 1966 ATM 145 United States Patent 3,460,124 SMOKE DETECTOR Randoiph J. Smith, Anaheim, and Kenneth R. House,

Norwalk, Calif., assignors to Interstate Engineering Corporation, Anaheim, Calif., a corporation of California Filed June 6, 1966, Ser. No. 555,424 Int. Cl. G081) 17/10, 21/00 U.S. Cl. 340-237 3 Claims ABSTRACT OF THE DISCLOSURE A smoke detector including a housing having an omnidirectional ambient smoke inlet and a central diffusion chamber into which is directed a light source and the reception path of a photoelectric cell, the housing having concentric bafiies with staggered interruptions uniformly distributed thereabout.

This invention relates to a smoke detector and more particularly to one which can be mounted quickly and conveniently in a home or other building structure.

It is an object of the invention to provide a smoke detector of compact, neat construction which can be mounted for example on a wall of a home and which is provided with two power sources, one an electrical connector which can be plugged into a Wall outlet, and a self-contained source, such as a battery, the latter functioning to energize the alarm even though the external power source is rendered inactive for some reason.

Another object is to provide a smoke detector which will actuate an alarm in the presence of smoke which will diffuse and reflect light from an internal light source to a detector such as a photoelectric cell, but which shields out external light Which might otherwise influence and activate the photoelectric cell.

A further object of the invention is to provide a smoke detector housing with smoke inlet passage means arranged to freely admit smoke from the exterior of the housing while at the same time providing a shield against the admission of external light.

A further object is to provide a light source Whose rays are shielded from the photoelectric cell in the absence of smoke but whose lighted condition can be determined by casual external visual inspection to show that it is lighted and in operative condition.

The above and other objects will more fully appear from the following description in connection with the accompanying drawings:

FIG. 1 is a perspective view of the housing;

FIG. 2 is an enlarged sectional view taken approximately on the line 2--2 of FIG. 1;

FIG. 3 is a sectional view taken approximately on the line 3-3 of FIG. 2;

FIG. 4 is a sectional view taken approximately on the line 4-4 of FIG. 2;

FIG. 5 is a diagram of the alarm circuit.

A housing H includes a main body portion 6, a rear panel 8, an intermediate shield unit and an outer shield unit 12.

The main body portion 6 has an outer wall portion 14 which slants inwardly from its outer edge and more sharply inwardly as at 16, the portion 16 being provided with apertures 18. The central portion of this wall includes a flat circular portion 20 having an inwardly extending socket 22 which support a lens 24. The lens 24 transmits light from a light source 26 in a casing 28 preferably formed integrally with the housing rear wall 8. This casing is provided with a removable cover plate 30. Light from the light source 26 passes through the lens 24 and 'ice through an aperture 32 and into a diffusion and reflection chamber 34 defined by a circular wall 36 having spaced cutouts 38.

The shield or baffle unit 10 is provided with an inwardly extending circular wall 40 which has spaced cut outs 42 which are staggered relative to the cutouts 38 in the outwardly concentric circular wall 36, and said walls 36 and 40 are spaced from each other so that smoke can enter through the spaced openings 38 of the Wall 36, flow between walls 36 and 40, and enter the diffusion and reflection chamber 34 through the spaced cutouts 42 of the inner circular wall 40. Formed integrally with the shield or baffle 10 and outwardly concentric to the circular walls 40 and 36, is a circular flange 44, and as shown in FIGS. 2 and 3, walls 36 and 40 and flange 44 define a tortuous smoke inlet 46, which in addition to the cutouts 38 and 42 permit smoke to enter the diffusion and reflection chamber 34.

The circular wall 40 is provided with a radially extending tubular socket 48 to receive a photoelectric cell 50 whose condensing lens 52 directs light from the diffusion and reflection chamber 34 to the photoelectric cell.

The shield or baffle 10, inwardly concentric to the circular wall 40, is provided with a wall 54 in the form of a conic section, the longer portion 56 of which is disposed toward the photoelectric cell 50.

The outer shield or baffle 12 is secured to the baffle 10 in spaced relation thereto by bosses 58 and screws or rivets 60 so that the baflies 12 and 10 define a smoke inlet passage indicated by the arrows 62. It will be noted that the bafiie 10 is likewise spaced from the inwardly slanting portion 15 of the front wall of the main body portion 6.

In the center of the baffle 12 is a piece of ruby glass 64 which lies on the axis of the conic section bafiie 54, the light aperture 32, lens 24 and the center of the light source 26. Thus, the ruby glass 62 is always illuminated by the light source 26. However, light from the source 26, when the diffusion chamber 34 is free of smoke, is not directed to the photoelectric cell 50 because the directed rays from the light source are at right angles to the axis of the photoelectric cell socket 48, and the photoelectric cell is disposed a substantial distance laterally of the beam of light issuing from the light source 26.

In the event of fire and/or smoke, smoke laden air can freely enter the diflusion and reflection chamber 34 between baffle 10 and the main body 6 of the housing H and thence through cutouts 38 and 42 and through the passage 46 around the edge of the circular wall 36. Smoke can also enter between the baffles 10 and 12 and through the frusto-conical sectional wall 54 to the interior of the diffusion and reflection chamber. Smoke in said chamber 34 will intercept the directional beam from the light source 26 and light will be diffused by and reflected from the smoke particles sufficient to activate the photoelectric cell 50 and energize the alarm to be described. However, by reason of the tortuous paths to which the entering smoke is subjected, it is impossible for external light to enter the diffusion and reflection chamber 34 and improperly activate the photoelectric cell.

Referring to FIG. 5, there is shown a transformer 66 having power connections 68 which may be plugged in by a suitable extension wire leading to an ordinary wall service outlet. One side of the transformer 66 is connected through the photoelectric cell 50 and amplifying diodes 68 and 70 which are in turn connected to the other side of the transformer induction coil 72. The light source 26 is shown also connected to both ends of the transformer coil 72. A variable resistance 72 is interposed between the diodes 68 and 70 and the two ends of the coil 72 so that the circuit can be properly adjusted relative to the photoelectric cell 50.

An alarm, such as a horn 76, is connected in the circuit through a relay 78 which is normally open, a manual circuit maker 80 is normally closed. In the presence of smoke in the diffusion and reflecting chamber 34, light will be transmitted to the photoelectric cell 50, reducing its resistance and permitting a stronger flow of current through the circuit to close the relay 78 and energize the audible signal 76.

A battery 82 is conveniently mounted within the housing H and connected across the horn 76 through the relay 78. This battery is also connected through the photoelectric cell 50 so that when light is reflected upon said cell, the battery 82 will close the relay 73 and energize the audible signal 76 even though the primary power source 68 may have been interrupted for some reason. The battery 82 is shown also connected in the circuit to lamp 26 so that if either the primary power source 68 or the battery 82 is operative, the lamp 26 will be lighted, but if both power sources are inoperative, lamp 26 is extinguished, indicating an inoperative condition of the alarm.

From the foregoing, it will be seen that we have provided a smoke detector which is compact in construction and can be mounted conveniently on the wall of a home or other building structure and which is rendered operative merely by placing a battery in the housing and plugging in the leads to the transformer 66 in a conventional wall outlet. In its operative condition, light from the lamp 26 is always present to indicate that condition, but the light is not diffused and reflected to the triggering photoelectric cell until there is smoke present in the diffusion and reflection chamber 34. The device is extremely reliable, its operative condition always being indicated by illumination of the ruby glass indicator 64 and the alarm being op erative either by current from the conventional 115 v. service in the home or by the self-contained battery in the alarm itself.

We claim:

1. A smoke detector comprising a housing, a central light diffusion chamber in said housing, a plurality of externally superimposed flanges having a central communicating means between said flanges to centrally communicate with said housing and said chamber, a plurality of housing wall portions surrounding said chamber, said wall .4 portions supporting said flanges and having a plurality of staggered apertures in the opposite walls of said wall portions to form an omni-directional ambient smoke inlet to said chamber to prevent external light from communicating with said chamber, said diffusion chamber being centered relative to said omni-directional inlet, a light source in said housing having a light path intersecting said diffusion chamber, a photoelectric cell in the housing shielded from direct undiffused rays from said light source and having a light reception path intersecting said diffusion chamber, the light reception path being so disposed relative to said diflfusion chamber and light source that said cell will be activated only by light diffused by smoke in said ditfusion chamber, and an alarm device connected to and activated by said photoelectric cell when the latter is activated.

2. The structure in claim 1, and said inlet for ambient smoke comprising housing wall portions defining a tortuous smoke passage from the interior of said difiusion chamber to the exterior of said housing, said housing wall portions having angularly disposed faces blocking the entrance of external light.

3. The structure in claim 1, and said housing having a first circular section with a light barrier comprising an interrupted wall, and a second circular section with a light barrier comprising an interrupted wall concentrically spaced from and generally coextensive with the interrupted wall of the first section, the interruptions of one wall being staggered relative to and overlapping those of the other wall to exclude external light.

References Cited UNITED STATES PATENTS 2,715,720 8/1955 Jenkins. 3,185,975 5/1965 Kompelien. 3,383,670 5/1968 Roberts.

JOHN W. CALDWELL, Primary Examiner DANIEL K. MYER, Assistant Examiner U.S. Cl. X.R. 

